At a typical oil and gas production site, a crude mixture from a well is brought to the surface and then separated into oil, gas and water in a three phase separator vessel. After separation, normally the oil goes to an oil storage tank, the water to a water tank and the natural gas to a natural gas pipeline.
Conventional separation systems leave a significant amount of natural gas entrained in the oil which flash vaporizes in the oil storage tanks. The natural gas that flash vaporizes in the storage tanks is contaminated by ambient air which decreases its economic value. This low value natural gas that has been contaminated is typically burned off at a combustion flare or vented directly to the atmosphere. Direct tank venting, fugitive emissions (gas leaks) from tanks, and exhaust from combustion flares significantly increases air pollution and greenhouse gasses, and wastes natural gas that could be recovered and sold.
Conventional approaches to processing hydrocarbon mixtures are inefficient at recovery of natural gas vapors and burn-off significant quantities of natural gas vapors. Some efforts have been made to reduce the burn-off or combustion flaring of natural gas vapors, such as U.S. Pat. Publ. No. 2013/0213085 to Ward (“Ward”). Ward discloses systems and methods for processing a hydrocarbon mixture wherein heat is generated from compression of recovered natural gas vapors and used to provide a heating medium for a heat exchanger. While some recovery efficiencies are realized through Ward's application of heat, the improvements are modest and not as effective as the method and system disclosed herein in which oil and condensate are processed on-site at low pressure or in a vacuum. Ward is incorporated herein by reference in its entirety.
U.S. Pat. No. 8,992,838 to Mueller (“Mueller”) discloses a method and system to reduce oxygen from flash vapor captured from storage tanks wherein the flash vapor is compressed and then refined in an oxygen reduction subsystem and sent to a sales line. While some oxygen is removed through Mueller's application of his subsystem, the effectiveness is modest in that oxygen is not entirely removed from the gas stream. In addition to modest oxygen reduction, byproducts are generated such as CO2 and H2O which are not economically viable products while the former is a greenhouse gas and the latter promotes corrosion in gas sales pipelines. In addition to byproducts, Mueller's system and method realizes poor efficiency due to H2S contamination which damages the catalyst bed. The method and system herein processes oil and condensate prior to the storage tanks, eliminating oxygen contamination by ambient air and eliminating the need for a specialized catalyst that can be damaged by H2S. Mueller is incorporated herein by reference in its entirety.
A system and method for oil and condensate on-site processing at an oil and gas production site is disclosed. The system comprises an oil and condensate distillation unit and a vapor recovery unit. In one embodiment, the oil and condensate distillation unit operates at low pressure or vacuum conditions to reduce the vapor pressure above the column of oil within the tubing, thereby increasing the production of oil and condensate and capturing entrained natural gas otherwise lost or burned off. In another embodiment, the oil and condensate distillation unit includes a Lease Automatic Custody Transfer unit. Benefits include improved quality and volume of recovered natural gas and decreased air pollution, in addition to increased oil and condensate production at the well site.